This publication is a synopsis of a number of studies and reports, undertaken since 2002, within the Assessment of Clean Energy Technologies (ACETECH) sector of the Clean Energies Unit of the Institute for Energy of the Directorate General Joint Research Centre. The Reports describe the present status of the technologies and their potential contribution to a sustainable EU strategy; explain the main issues affecting their innovation potential, drawing attention to barriers and opportunities; discuss options for enhancing their perspectives; and reflect on policy and strategic developments, including international collaboration, for realisation of such technologies. The ensemble of work offers a shared basis of knowledge and understanding, and provides sound information, quantitative and qualitative, to accompany the energy-related policy making processes of the European Union.